This laboratory will conduct studies in three areas: (1) Adrenal Mitochondrial Hydroxylation: We will continue to study the mechanism of electron transport through adrenodoxin, adrenodoxin reductase, and the cytochromes P-450 engaged in 11 beta hydroxylation and in side chain cleavage. Our chief objectives are to delineate the mechanism of electron transport both in the soluble system and in the membrane, and to initiate studies of the biological control of these enzymes. (2) Adrenal Microsomal Hydroxylation: We are initiating studies on the adrenal microsonal hydroxylation system, which appears to include a flavoprotein similar to that of liver microsomes, and does not require an iron-sulfur protein for electron transport to cytochrome P-450. We will examine the mechanism of electron transport and the biological rol of this enzyme. (3) Nitrite Reductase of Spinach: This enzymes has been shown by our laboratory to be an iron-sulfur protein containing siroheme. We have now accumulated evidence that the iron-sulfur center may be an Fe4-S4 rather than an Fe2-S2 grouping. We are presently engaged in repeating previous prosthetic group analysis, and emphasizing EPR studies. In the coming year, we expect to make extensive use of EPR, freeze-quench, and stopped-flow studies to examine the mechanism whereby this enzyme, which seems to have the capacity to transport one electron at a time, can catalyze the 6-electron reduction of nitrite to ammonia.